Date   
Re: 2245A mains filtering

Brian Cockburn
 

Chuck,

Maybe I'll just stop worrying.

Thanks, Brian.

5L4N Calibration Frustration

Jason A.
 

Hello All,

I've finally found a pair of 5000-series extension cables and went through the calibration process for my 5L4N. Once I had everything working as it should, I reinstalled all the shielding and screws to get it ready to go back in the mainframe and thought I had better try it one more time before calling it a day. Everything was all out of whack again - from the timing on the sweep to what the sweep was displaying. So I pulled all the screws out, took the shields off, opened it back up and depending on how I had things opened up (left panel in place, right panel open at 90 degrees, etc.), it would operate in varying accuracy levels.

I then started poking around at the various wiring harnesses and coax running through and found moving those made no difference. Applying a jumper ground from various portions of the chassis to other ground points didn't seem to make any difference either. I then used a chop-stick to apply gentle pressure on the boards where it looked like the wires may have pushed up against them and looked for any caps that might get bent over when the sides are closed. No difference.

What am I missing?!

Thanks and best regards,

Jason

Re: 2445 CH2 Amplitude is 1/3 of expected value

Jay H. <jcholsap@...>
 

THanks, Siggi,
I thought about trying something like that just as a matter of isolating the problem from the outside. But I'm a bit overwhelmed with work and family right now and once I start troubleshooting I usually keep at it. And that perfect multiple of 3 really nags at me. Call it intuition, the force, upset stomach,... But for next time, I am noticing a "pots" theme with these old o-scopes which isn't surprising without gold plated contacts.
Cheers,
Jay

Re: Back from vacation

Jason A.
 

Hi Dennis,

I have been combing through the posts here and didn't see where I would be able to get one of your boards. I have a 7CT1N and plan to make the power supplies and tube plugin boards myself (I have a Jackson 658A which is allegedly a dynamic mutual conductance tester, or Dynamic Output as they phrase it, but due to its layout it would be very difficult to modify per your article).

Please hold me to task if you see anything here that is a red-flag to you... :-)

I have a plethora of transformers, tube sockets, project boxes and sundry parts to make it all happen, so that part doesn't daunt me (unless I missed something along the way). I plan to use one of these with a variable resistor for the screen supply: http://www.antiquewireless.org/uploads/1/6/1/2/16129770/37-a_solid-state_filter_choke_or_field_coil_replacement.pdf - that should do the trick of getting anywhere up to the 300+V screen values you mentioned in your article. In fairness, I only plan on testing small signal tubes in either Octal, Noval, or B7G, so that limits the number of sockets I would need to wire up. I have a 0-30V, 0-3A supply that could work well for filaments. I don't see why a couple of wall warts couldn't be used for the -50 and +6V supplies - I have a 48v 500mA as well as several 6V ones in my parts bin and I have a feeling that would be close enough for my purposes.

If you don't see anything wrong with my plans, having your board would certainly make things easier from that standpoint, but I could always proto-board something together otherwise.

Thanks for showing a good way to do this! Thankfully I have a 7834, so I can even use the screen memory to compare sections.

Thanks again and best regards,

Jason

Re: PS2520 aka GW Instek PPT-3615

Ken Eckert
 

Hi;

I know this is an old thread, I have just uploaded the schematics, calibration procedure and op/prog manuals for the PS2520G and PS2521G aka GW Instek PPT-3615 and PPS-1830 (and possibly PPE-3323) to KO44b and the Boat Anchor Manual Archive sites.
Ken

Re: PS2520 aka GW Instek PPT-3615

Siggi
 

Hey Ken,

Thanks for digging those up. Do you happen to remember where these
surfaced? Just curious...

Now that I’ve seen the calibration procedure, I wonder if perhaps over
zealous hi-pot testing was the cause for mine suffering damage in three
galvanically isolated domains.

Siggi

On Tue, Jul 16, 2019 at 16:32 Ken Eckert <eckertkp@...> wrote:

Hi;

I know this is an old thread, I have just uploaded the schematics,
calibration procedure and op/prog manuals for the PS2520G and PS2521G aka
GW Instek PPT-3615 and PPS-1830 (and possibly PPE-3323) to KO44b and the
Boat Anchor Manual Archive sites.
Ken



P6201 dc current measurements

John
 

I have a P6201 active FET probe which I suspect is damaged. I bought it when I got a 7934 mainframe. Anyway I have measured the DC voltages and they are all OK. However I am concerned that R298 on the DC-LF Amplifier board gets very hot to the touch. It drops the +15V to +7V and I lifted the leg of one end and it has 98 ma running through it and that equates to almost 3/4 of a watt. That seems excessive. So I checked C240 and it is OK. I then lifted the +7V line going to the probe and it is drawing about 21 ma. So the question is a) is this current draw normal? And b) if not is there an easy way to separate the boards so I can find out which section is drawing the unusual amount of current? There is nothing in the manual or the schematics to indicate what the right current draw should be. Given that the +7v line is correct the R298 seems to be the right value (78 ohms) and has the right current flowing through it but the fact that it gets hot indicates its power dissipation is under rated for the job it is doing. Or is this Tektronix way of demoisurising the housing (joke here).

John
VK2DLP

Re: P6201 dc current measurements

george edmonds
 

Hi John

A 6201 draws approximately 105ma from the +15vdc supply and 110ma from the -15vdc supply with a total power dissipation of 3.2W . These figures are from the Tektronix manual.

73 George G6HIG On Wednesday, July 17, 2019, 10:46:20 AM GMT+1, John <@VK2DLP> wrote:

I have a P6201 active FET probe which I suspect is damaged. I bought it when I got a 7934 mainframe. Anyway I have measured the DC voltages and they are all OK. However I am concerned that R298 on the DC-LF Amplifier board gets very hot to the touch. It drops the +15V to +7V and I lifted the leg of one end and it has 98 ma running through it and that equates to almost 3/4 of a watt. That seems excessive. So I checked C240 and it is OK. I then lifted the +7V line going to the probe and it is drawing about 21 ma. So the question is a) is this current draw normal? And b) if not is there an easy way to separate the boards so I can find out which section is drawing the unusual amount of current? There is nothing in the manual or the schematics to indicate what the right current draw should be. Given that the +7v line is correct the R298 seems to be the right value (78 ohms) and has the right current flowing through it but the fact that it gets hot indicates its power dissipation is under rated for the job it is doing. Or is this Tektronix way of demoisurising the housing (joke here).

John
VK2DLP

Re: P6201 dc current measurements

Craig Sawyers
 

Looking at the schematic, the input FET runs at Idss, which is in the range 5-15mA. So the drain is at
0V. That sets the next transistor current to (7-0.7)/510 = 12mA and the second transistor to
(7-1.4)/300 = 18mA (rounding numbers). So the probe body will pull 35-45mA.

But the 7V also runs the output amplifier Q300/Q320, which I calculate roughly draws 14mA.

So I would expect the total drain on the 7V line to be between 49mA and 59mA, so the dissipation in
R298 should be 0.47W maximum. That resistor is a wirewound 1W rated part and so should be OK, but will
certainly run hot - probably too hot to touch, and should be spaced above the board to allow air
circulation.

Craig

Subject: [TekScopes] P6201 dc current measurements

I have a P6201 active FET probe which I suspect is damaged. I bought it when I got a 7934 mainframe.
Anyway I have measured the DC voltages and they are all OK. However I am concerned that R298 on
the DC-LF Amplifier board gets very hot to the touch. It drops the +15V to +7V and I lifted the leg
of
one end and it has 98 ma running through it and that equates to almost 3/4 of a watt. That seems
excessive. So I checked C240 and it is OK. I then lifted the +7V line going to the probe and it is
drawing
about 21 ma. So the question is a) is this current draw normal? And b) if not is there an easy way
to
separate the boards so I can find out which section is drawing the unusual amount of current? There
is
nothing in the manual or the schematics to indicate what the right current draw should be. Given
that
the +7v line is correct the R298 seems to be the right value (78 ohms) and has the right current
flowing
through it but the fact that it gets hot indicates its power dissipation is under rated for the job
it is
doing. Or is this Tektronix way of demoisurising the housing (joke here).

John
VK2DLP

Re: P6201 dc current measurements

Craig Sawyers
 

Not in my manual it isn't.

Craig

Hi John

A 6201 draws approximately 105ma from the +15vdc supply and 110ma from the -15vdc supply with a
total power dissipation of 3.2W . These figures are from the Tektronix manual.

73 George G6HIG On Wednesday, July 17, 2019, 10:46:20 AM GMT+1, John
<@VK2DLP> wrote:

I have a P6201 active FET probe which I suspect is damaged. I bought it when I got a 7934
mainframe.
Anyway I have measured the DC voltages and they are all OK. However I am concerned that R298 on
the DC-LF Amplifier board gets very hot to the touch. It drops the +15V to +7V and I lifted the leg
of
one end and it has 98 ma running through it and that equates to almost 3/4 of a watt. That seems
excessive. So I checked C240 and it is OK. I then lifted the +7V line going to the probe and it is
drawing
about 21 ma. So the question is a) is this current draw normal? And b) if not is there an easy way
to
separate the boards so I can find out which section is drawing the unusual amount of current? There
is
nothing in the manual or the schematics to indicate what the right current draw should be. Given
that
the +7v line is correct the R298 seems to be the right value (78 ohms) and has the right current
flowing
through it but the fact that it gets hot indicates its power dissipation is under rated for the job
it is
doing. Or is this Tektronix way of demoisurising the housing (joke here).

John
VK2DLP

Re: P6201 dc current measurements

george edmonds
 

Hi Craig

Try this link,

http://w140.com/tek_p6201.pdf and look at page 8

73 George G6HIG

On Wednesday, July 17, 2019, 12:24:26 PM GMT+1, Craig Sawyers <c.sawyers@...> wrote:

Not in my manual it isn't.

Craig

  Hi John

A 6201 draws approximately 105ma from the +15vdc supply and 110ma from the -15vdc supply with a
total power dissipation of 3.2W . These figures are from the Tektronix manual.

73 George G6HIG    On Wednesday, July 17, 2019, 10:46:20 AM GMT+1, John
<@VK2DLP> wrote:

  I have a P6201 active FET probe which I suspect is damaged. I bought it when I got a 7934
mainframe.
Anyway I have measured the DC voltages and they are all OK. However I am concerned that R298 on
the DC-LF Amplifier board gets very hot to the touch. It drops the +15V to +7V and I lifted the leg
of
one end and it has 98 ma running through it and that equates to almost 3/4 of a watt. That seems
excessive. So I checked C240 and it is OK. I then lifted the +7V line going to the probe and it is
drawing
about 21 ma. So the question is a) is this current draw normal? And b) if not is there an easy way
to
separate the boards so I can find out which section is drawing the unusual amount of current? There
is
nothing in the manual or the schematics to indicate what the right current draw should be. Given
that
the +7v line is correct the R298 seems to be the right value (78 ohms) and has the right current
flowing
through it but the fact that it gets hot indicates its power dissipation is under rated for the job
it is
doing. Or is this Tektronix way of demoisurising the housing (joke here).

John
VK2DLP

Re: 2247A PSU Troubleshooting

Darren Ting
 

Hi chipbee40

I am having this same issue. first power on PSU with FAN connected, it start spin 2-3 seconds then stop.

Preregulator circuit look fine and 44V rail also fine [my measurement read 41v should be close enough].

something wrong when measure Q2214 gate voltage should be 5v, but I get hard on 20V

I had measure and test following component but still hit the wall can't find any faulty part.

C2210 (4.7uF 100v) --Checked no issue, also replaced just to eliminate this
Q2209 and Q2210 (TIP32C) out of circuit --Checked no issue, both good reading
Q2214 (Mosfet) out of circuit --checked no issue either
All diode/zener checked no short
All resister checked no open either
Q2212 and Q2213 out of circuit checked no issue

Some cross resistor or zener volt measurement:-
R2205 = 27V
R2246 = 13.8V
VR2205 = 6.1V
R2233 = 35V
R2237 = 36.6V
R2240 = 0.6V
R2274 = 0V
R2241 = 5V
R2239 = 0.3V
R2252 = 0.7V
R2238 = 2.28
R2270 = 5.4V
R2236 = 20V
R2232 = 0V
Q2213 Vbc = 40V

I am suspecting some fault in area "PREREGULATOR OUTPUT VOLTAGE CONTROL" or "INVERTER CONTROL" but can't really find which component.

Any member here could pin point potential fault in this case?
The circuit look simple enough yet can't find faulty part causes it.

Re: P6201 dc current measurements

 

John:

I have 4 of these P6201 probes and in all R298 runs HOT! When I have the covers off of the Amplifier Box for adjusting and every time I touch R298 accidentally I jump a foot because of the temp of that resistor. I know it is HOT but accidentally touching it is a surprise and my reflex reaction is to pull back.
So you don't have a problem from R298 running hot.
Bill

Re: P6201 dc current measurements

John
 

Thanks for the experienced based info. I did the same and when I am looking at electronics hot usually means something is wrong. I guess I should just go through the calibration procedure and make sure everything is in spec. Thanks to all who responded. Experience beats conjecture every time.

John
VK2DLP

Re: 2247A PSU Troubleshooting

Darren Ting
 

Hi Members,

Just to add on new finding, when first power on this PSU with FAN connected, I did hear HISS sound when FAN is running but disappear after 2-3 seconds. Even without FAN connected this HISS sound also present.

Could this be short circuit somewhere or this consider normal while initially coil is charging up Caps with higher Amp causes transfer generate HISS sound?

2465 - No trigger no trace...

Chris Don
 

Hi,
A weird issue on one of my 2465: No trigger no trace...
As soon as trigger locks (including on a channel not selected for display), the traces are displayed properly and everything works OK.
But if trigger doesn't lock, absolutely NO trace is displayed.
Does this issue ring a bell to anyone?
Thanks
Chris

Re: 2465 - No trigger no trace...

Chuck Harris
 

There are really only a couple of choices:

1) bad trigger hybrid
2) bad MUX/OPAMP/Sample Capacitor.

Trigger hybrids are one of the new show stoppers
for the 2465 family.

-Chuck Harris

Chris Don wrote:

Hi,
A weird issue on one of my 2465: No trigger no trace...
As soon as trigger locks (including on a channel not selected for display), the traces are displayed properly and everything works OK.
But if trigger doesn't lock, absolutely NO trace is displayed.
Does this issue ring a bell to anyone?
Thanks
Chris

Re: 2465 - No trigger no trace...

ppppenguin
 

I know this is a silly question, but what trigger mode have you selected? If it's "Normal" then you don't get a trace in the absence of triggering.

Re: 2465 - No trigger no trace...

Chuck Harris
 

Actually not silly at all. I think we as a group tend
to assume that most folks here know how to use a scope...
but that isn't always the case.

NORMAL trigger mode, would seem to be, normal, but in
truth, most scope use gets done in AUTO LVL, or AUTO mode.

-Chuck Harris

ppppenguin wrote:

I know this is a silly question, but what trigger mode have you selected? If it's "Normal" then you don't get a trace in the absence of triggering.



Re: 2467B rear feet repros and other parts?

radioconnection@...
 

Craig, tried emailing you to your COX email address, but no luck reaching you? Not sure I have to correct email?